1. Field of Invention:
This invention relates generally to tools used to manufacture precision steel parts by a grinding process. In particular, it relates to tools for reforming and reconditioning an abrasive wheel which in turn imparts dimensional characteristics to a part piece of steel or of other hard material being precision ground by the abrasive wheel
2. Description of the Prior Art
A rotary dressing tool is a cylindrical wheel whose periphery across the axial plane is profiled such that upon rotational contact with an abrasive wheel, the perimeter surface of the abrasive wheel will conform to the shape of the rotary dressing tool. The shape of the rotary dressing tool is manufactured to the geometric specification standard of a given part piece desired by a customer. After contact with the rotary dressing tool, the abrasive wheel is conditioned for utilization as a machining medium for production in quantity of the desired part piece.
Surprisingly, natural diamonds are not efficient in directly cutting profiles in part piece of steel. However, diamonds can be used effectively to impart intricate profiles to an abrasive (grit) wheel which in turn is very efficient in cutting a desired profile in the steel part piece. Conventional diamond dressing tools normally afford between 12,000 and 70,000 dresses before requiring return to the tool manufacturer for reconditioning the tool. The present invention utilizes not only randomly dispersed natural or synthetic diamond particles but preformed polycrystalline diamond segments as well. The segments are symmetrically or randomly placed about the periphery of the rotary dressing tool, in addition to the dispersed diamond particles, to enhance the operational life of the tool. Tests of the present invention have revealed a three-fold increase of dressing capacity, producing as many as 207,000 dresses before reconditioning was required.
Historically, two methods have been used to manufacture rotary dressing tools: (a) powdered metal sintered to hardness as a tool and (b) electroforming. Powered metal tools, although offering high resistance to abrasive actions of a grinding wheel, have serious limitations. Using such tools you cannot produce radii smaller than 0.005 inches. Thus, you cannot produce the intricate forms often required by the specifications of the customer. Also the use of the powdered metal tools depends upon the availability of suitable diamond reenforcements. You must use natural diamond reenforcements due to the sintering temperatures to which these tools are subjected during their manufacturing process.
On the other hand, rotary dressing tools manufactured by the electroforming process, where the diamond particles are electrically deposited on a nickel alloy trueing wheel, can be produced with extremely fine radii and very intricate geometries. However, smaller diamond particles must be used and the nickel alloy matrix holding the diamonds is less abrasive resistant to the abrasive wheel than the sintered powdered metal dressing tool. The latter considerations, of course, shorten the operational life of the dressing tool. Also, it is difficult to use natural diamond reenforcements because the irregular shape of natural diamond reenforcements does not facilitate the proper placement of the diamonds required for intricate cutting patterns.
The present invention addresses the problems of the prior art and combines the advantages of electroformed dressing tools with the enhanced abrasive resistance offered by the use of polycrystalline synthetic diamond segments. Also, the use of the segments permits the tool to be pre-profiled by a traveling wire e.d.m. (electrical discharge machine) to accommodate the most demanding and intricate grinding patterns.